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Atherosclerosis: Difference between revisions
→Initiation and formation of atherosclerotic plaque
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=== Initiation and formation of atherosclerotic plaque === | === Initiation and formation of atherosclerotic plaque === | ||
[[File: | [[File:Figure_7_-_Fatty_streak_formation_revealing_platelet_aggregation_on_the_endothelial_surface.png|right|thumb|Figure 7. Fatty streak formation]] | ||
The earliest visible signs of atherogenesis are the fatty streak and pre-existing lesions of adaptive intimal thickening. Fatty streak is yellow discoloration on the surface of the artery lumen, which is flat or slightly elevated in the intima and contains accumulations of intracellular and extracellular lipid. At this stage of initiation, the fatty streak doesn’t protrude substantially into the artery wall nor impede blood flow. This process is already visible in most people by the age of 20. At this stage, there are no symptoms and this lesion may even diminish over time. Initiation of fatty streak development is most likely caused by endothelial dysfunction, since it involves entry and modification of lipids within the subintima. This modified layer of lipids creates a proinflammatory environment and initiates the migration of leukocytes and formation of foam cells (Figure 7). Intimal thickening mainly contains smooth muscle cells and proteoglycan-collagen matrix with a few or no infiltrating inflammatory cells.<br /> | The earliest visible signs of atherogenesis are the fatty streak and pre-existing lesions of adaptive intimal thickening. Fatty streak is yellow discoloration on the surface of the artery lumen, which is flat or slightly elevated in the intima and contains accumulations of intracellular and extracellular lipid. At this stage of initiation, the fatty streak doesn’t protrude substantially into the artery wall nor impede blood flow. This process is already visible in most people by the age of 20. At this stage, there are no symptoms and this lesion may even diminish over time. Initiation of fatty streak development is most likely caused by endothelial dysfunction, since it involves entry and modification of lipids within the subintima. This modified layer of lipids creates a proinflammatory environment and initiates the migration of leukocytes and formation of foam cells (Figure 7). Intimal thickening mainly contains smooth muscle cells and proteoglycan-collagen matrix with a few or no infiltrating inflammatory cells.<br /> | ||
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Another major factor that can impair the atheroprotective endothelial function is chemical irritants such as cigarette smoking, abnormally high circulating lipid levels and high sugar levels (diabetes mellitus). They can contribute to endothelial dysfunction and are all well- known risk factors for atherosclerosis. Exposure to chemical irritants promotes endothelial dysfunction by increasing endothelial production of reactive oxygen species, which alter the metabolic and synthetic functions of endothelial cells. As a result, the endothelium is inclined to exhibit proinflammatory processes, such as secreting inflammatory cytokines.<br /> | Another major factor that can impair the atheroprotective endothelial function is chemical irritants such as cigarette smoking, abnormally high circulating lipid levels and high sugar levels (diabetes mellitus). They can contribute to endothelial dysfunction and are all well- known risk factors for atherosclerosis. Exposure to chemical irritants promotes endothelial dysfunction by increasing endothelial production of reactive oxygen species, which alter the metabolic and synthetic functions of endothelial cells. As a result, the endothelium is inclined to exhibit proinflammatory processes, such as secreting inflammatory cytokines.<br /> | ||
[[File:Figure_8_-_Endothelial_dysfunction_-_Leukocyte_adhesion_and_migration_into_the_deep_layer_of_the_intima.png|thumb|right|Figure 8. Endothelial dysfunction: Leukocyte adhesion and migration into the deep layer of the intima.]] | |||
In conclusion, hemodynamic and chemical stressors contribute to disturbance of the endothelial homeostasis and promote endothelial dysfunction. This results in impairment of permeability barrier function, secretion of inflammatory cytokines, stimulation of adhesion molecules on the cell surface that promote leukocyte recruitment, and altered antithrombotic properties and release of vasoactive molecules ( | In conclusion, hemodynamic and chemical stressors contribute to disturbance of the endothelial homeostasis and promote endothelial dysfunction. This results in impairment of permeability barrier function, secretion of inflammatory cytokines, stimulation of adhesion molecules on the cell surface that promote leukocyte recruitment, and altered antithrombotic properties and release of vasoactive molecules (Figure 8). Consequently, these effects establish the groundwork for further advancement of atherosclerosis.<br /> | ||
==== ''Lipoprotein entry and modification'' ==== | ==== ''Lipoprotein entry and modification'' ==== | ||